STRUCT IIO_DEV_OPAQUE(9)

💅 struct iio_dev_opaque(9) — the kernel API manual, but make it make sense 🎀

okay so bestie, gather round, because we're diving into the industrial I/O device opaque information struct, aka struct iio_dev_opaque — and honestly? it's giving "secret sauce that runs the whole vibe" energy. let's get into it ✨

✨ SYNOPSIS ✨

struct iio_dev_opaque {
    struct iio_dev                  indio_dev;
    int currentmode;
    int id;
    struct module                   *driver_module;
    struct mutex                    mlock;
    struct lock_class_key           mlock_key;
    struct mutex                    info_exist_lock;
    struct lock_class_key           info_exist_key;
    bool trig_readonly;
    struct iio_event_interface      *event_interface;
    struct iio_buffer               **attached_buffers;
    unsigned int                    attached_buffers_cnt;
    struct iio_ioctl_handler        *buffer_ioctl_handler;
    struct list_head                buffer_list;
    struct list_head                channel_attr_list;
    struct attribute_group          chan_attr_group;
    struct list_head                ioctl_handlers;
    const struct attribute_group    **groups;
    int groupcounter;
    struct attribute_group          legacy_scan_el_group;
    struct attribute_group          legacy_buffer_group;
    void *bounce_buffer;
    size_t bounce_buffer_size;
    unsigned int                    scan_index_timestamp;
    clockid_t clock_id;
    struct cdev                     chrdev;
    unsigned long                   flags;
  #if defined(CONFIG_DEBUG_FS);
    struct dentry                   *debugfs_dentry;
    unsigned int                    cached_reg_addr;
    char read_buf[20];
    unsigned int                    read_buf_len;
  #endif;
};

like, look at all those fields. it's a whole aesthetic. 🦋

🌸 Members 🌸

okay so this is the part where we go field by field, no skips, no cap. every single one matters. let's go 🔥

• indio_dev — the public industrial I/O device info. this is the part everyone gets to see, the main character if you will 👑
• currentmode — the operating mode it's in right now! drivers may eventually peek at this, but bestie, treat it as read-only — it's a core internal bit, iykyk 💅
• id — used to identify the device internally. the internal little name tag 🏷️
• driver_module — used to make it harder to undercut users. yes, it's a whole protective vibe 🫶
• mlock — a lock that stops simultaneous device state changes. no two things touching the state at once, periodt 🚫
• mlock_key — the lockdep class for the iio_dev lock. very "sorted, organized, iconic" of it 🎀
• info_exist_lock — a lock to prevent use during removal. don't touch it while it's leaving, that's rude 😭
• info_exist_key — the lockdep class for the info_exist lock. matching set, slay ✨
• trig_readonly — marks the current trigger immutable. it's frozen, don't come for it 🧊
• event_interface — the event chrdevs associated with interrupt lines. the interrupt-line besties 🌈
• attached_buffers — an array of buffers statically attached by the driver. the pre-attached crew 🍓
• attached_buffers_cnt — how many buffers are in that statically attached array. the headcount, literally 🔢
• buffer_ioctl_handler — the ioctl handler for this IIO device's buffer interface. its personal handler, obsessed 💖
• buffer_list — a list of all buffers currently attached. the group chat of buffers 📋
• channel_attr_list — keeps track of automatically created channel attributes. the auto-tracker, so organized 🗂️
• chan_attr_group — the group for all attrs in the base directory. base directory gang 💜
• ioctl_handlers — ioctl handlers registered with the core handler. the registered ones, very official 🎀
• groups — attribute groups. just groups, simple and iconic 🌸
• groupcounter — the index of the next attribute group. the "what's next" counter 🔢
• legacy_scan_el_group — the attribute group for the legacy scan elements attribute group. legacy but still serving 🫶
• legacy_buffer_group — the attribute group for the legacy buffer attributes group. also legacy, also iconic 🦋
• bounce_buffer — for devices that call iio_push_to_buffers_with_ts_unaligned. that's the whole vibe, no notes ✨
• bounce_buffer_size — the size of the currently allocated bounce buffer. how big the bounce is, bestie 📏
• scan_index_timestamp — a cache of the index to the timestamp. cached so it's fast, we love efficiency ⚡
• clock_id — the timestamping clock posix identifier. its posix ID, very official 💅
• chrdev — the associated character device. the char device bestie 🔌
• flags — file ops related flags, including the busy flag. flags with a busy one in there, note it 🚩
• debugfs_dentry — the device-specific debugfs dentry. debugfs but make it specific 🐞
• cached_reg_addr — the cached register address for debugfs reads. cached for the reads 📌
• read_buf — the read buffer used for the initial reg read. the initial-read buffer, literally 📖
• read_buf_len — the data length in read_buf. how much is in the buffer 🔢

👑 SEE ALSO 👑

okay so if you wanna go deeper (and you should, bestie), check out the kernel file ./include/linux/iio/iio-opaque.h — that's the source of truth, fr fr 🌟

and that's the whole thing! hope this made the opaque struct feel a little less opaque 💖 you're doing amazing, sweetie. go forth and read those headers 🦋

source: ./include/linux/iio · date: October 2026 · this has been your kernel struct explainer, signing off ✨